It is disclosed in the above-identified patent application Ser. No. 569,738 that useful hydroformylation catalysts can be prepared by introducing into the hydroformylation reaction zone a mixture of (a) a disubstituted ferrocene and (b) a Group VIII compound as exemplified by the following: ##STR2## wherein M is a Group VIII metal, preferably rhodium; Q is phosphorus, arsenic, or antimony, preferably phosphorus; and R is phenyl or a lower alkyl group, preferably phenyl.
The catalytic complex resulting from the above-summarized combination (or from equivalent formulations also discussed in said application Ser. No. 569,738) is, broadly speaking, a complex cyclic structure containing one mole of the above-described substituted ferrocene and one mole of the above-described Group VIII compound.
It has now been discovered, however, that, although the catalyst formed by reacting one mole of ferrocene derivative with one mole of Group VIII (e.g., rhodium) derivative as described above can be employed as a hydroformylation catalyst, the best results obtained in working with complexes of this general type are with formulations in which the molar ratio of ferrocene derivative to Group VIII metal is 1.5:1 rather than 1:1. This has led to the realization that the optimum catalyst in these ferrocene-derived complexes is a different one from those previously envisioned. It is a more complicated molecule, as will be further explained hereinbelow, although the procedures for forming it and for employing it in hydroformylation reactions are closely related to those used in preparing the 1:1 molar ratio complexes.